The concept of ‘environmental health’ of our inland water systems considers our rivers, wetlands and groundwater systems as ecological systems, including flora and fauna and their habitats, and the linkages between water systems and their catchments and climate. The health of inland water systems depends on their capacity to support key environmental functions (temperature regulation, nutrient and carbon cycling, salt balance and sediment transport) and to support communities and populations of native species.
A healthy system is one that has retained its character, biodiversity and functions over time and is more resilient than a system with deteriorated health to pressures and changes in environmental conditions, including climate change, resource use, pollution and invasive pests.7
The health of our inland water systems is relative. We need to ask: relative to what? There are no generally applicable benchmarks for the diverse ecosystem functions and species that make up inland water ecosystems. Instead, ecological assessments generally use a ‘reference condition’ with which actual conditions are compared. This reference is normally the state of the ecosystem with no history of human disturbance.8-9
The assessment in this report recognises that, since humans have shaped the condition of our inland waters for more than 50 000 years, it is not possible or appropriate to separate Aboriginal influences from such a reference condition. The same conclusion was drawn for a North American application, in which Native American influences on the ecosystem were considered as integral to the ecological reference condition.10 Therefore, for the purposes of this assessment, the reference condition of the health of our inland water systems is their condition before European settlement.
The use of this benchmark does not imply that we should restore inland water ecosystems to their near-original condition—it is simply the condition from which we measure change where we can.
A review of all state and national environmental programs determined that no suitable, single ecological indicator of water stress was readily available.11 In this assessment, we look at the major dimensions of the state and trend of our inland water ecosystems:
- how the flows and levels of water in our environment have changed
- how the quality of water in our environment has changed
- how ecological processes and species populations have changed.